scholarly journals Kinematics around the B335 protostar down to au scales

2019 ◽  
Vol 631 ◽  
pp. A64 ◽  
Author(s):  
Per Bjerkeli ◽  
Jon P. Ramsey ◽  
Daniel Harsono ◽  
Hannah Calcutt ◽  
Lars E. Kristensen ◽  
...  
Keyword(s):  
Morphological Properties ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Small Scale ◽  
Short Baseline ◽  
Stellar Objects ◽  
Spatially Resolved ◽  
Long Baseline ◽  
The Relationship ◽  
The Continuum

Context. The relationship between outflow launching and the formation of accretion disks around young stellar objects is still not entirely understood, which is why spectrally and spatially resolved observations are needed. Recently, the Atacama Large Millimetre/sub-millimetre Array (ALMA) carried out long-baseline observations towards a handful of young sources, revealing connections between outflows and the inner regions of disks. Aims. Here we aim to determine the small-scale kinematical and morphological properties of the outflow from the isolated protostar B335 for which no Keplerian disk has, so far, been observed on scales down to 10 au. Methods. We used ALMA in its longest-baseline configuration to observe emission from CO isotopologues, SiO, SO2, and CH3OH. The proximity of B335 provides a resolution of ~3 au (0.03′′). We also combined our long-baseline data with archival observations to produce a high-fidelity image covering scales up to 700 au (7′′). Results. 12CO has an X-shaped morphology with arms ~50 au in width that we associate with the walls of an outflow cavity, similar to what is observed on larger scales. Long-baseline continuum emission is confined to <7 au from the protostar, while short-baseline continuum emission follows the 12CO outflow and cavity walls. Methanol is detected within ~30 au of the protostar. SiO is also detected in the vicinity of the protostar, but extended along the outflow. Conclusions. The 12CO outflow does not show any clear signs of rotation at distances ≳30 au from the protostar. SiO traces the protostellar jet on small scales, but without obvious rotation. CH3OH and SO2 trace a region <16 au in diameter, centred on the continuum peak, which is clearly rotating. Using episodic, high-velocity, 12CO features, we estimate the launching radius of the outflow to be <0.1 au and dynamical timescales of the order of a few years.

scholarly journals A Search for Disks around Massive Young Stellar Objects

2004 ◽  
Vol 221 ◽  
pp. 425-430 ◽  
Author(s):  
A. G. Gibb ◽  
M. G. Hoare ◽  
L. G. Mundy ◽  
F. Wyrowski
Keyword(s):  
Near Infrared ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Circumstellar Disk ◽  
Mass Yield ◽  
Stellar Objects ◽  
Strong Emission ◽  
Yield Values ◽  
Infrared Data ◽  
The Continuum

We present subarcsecond observations at 2.7 and 1.4 mm of a sample of massive young stellar objects made with the BIMA millimetre array. For most sources the continuum emission on the smallest scales at 2.7 mm is dominated by free-free emission from the stellar wind or jet. Strong emission at 1.4 mm shows the presence of significant dust associated with Cep A and GL 490 but our resolution is not sufficient to resolve any structure. The 2.7-mm emission from GL 490 is resolved but it is not clear whether we are seeing a single circumstellar disk or a secondary companion, although near-infrared data support the disk hypothesis. Estimates of the dust mass yield values of ∼1–4 M⊙ within radii of 150 to 1000 AU.

scholarly journals Accretion Signatures on Massive Young Stellar Objects

2014 ◽  
Vol 9 (S307) ◽  
pp. 431-436
Author(s):  
F. Navarete ◽  
A. Damineli ◽  
C. L. Barbosa ◽  
R. D. Blum
Keyword(s):  
Massive Star ◽  
Narrow Band ◽  
Massive Stars ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Stellar Clusters ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
Low Mass ◽  
The Continuum

AbstractWe present preliminary results from a survey of molecular H2 (2.12 μm) emission in massive young stellar objects (MYSO) candidates selected from the Red MSX Source survey. We observed 354 MYSO candidates through the H2 S(1) 1-0 transition (2.12 μm) and an adjacent continuum narrow-band filters using the Spartan/SOAR and WIRCam/CFHT cameras. The continuum-subtracted H2 maps were analyzed and extended H2 emission was found in 50% of the sample (178 sources), and 38% of them (66) have polar morphology, suggesting collimated outflows. The polar-like structures are more likely to be driven on radio-quiet sources, indicating that these structures occur during the pre-ultra compact H ii phase. We analyzed the continuum images and found that 54% (191) of the sample displayed extended continuum emission and only ~23% (80) were associated to stellar clusters. The extended continuum emission is correlated to the H2 emission and those sources within stellar clusters does display diffuse H2 emission, which may be due to fluorescent H2 emission. These results support the accretion scenario for massive star formation, since the merging of low-mass stars would not produce jet-like structures. Also, the correlation between jet-like structures and radio-quiet sources indicates that higher inflow rates are required to form massive stars in a typical timescale less than 105 years.

scholarly journals The GRAVITY young stellar object survey

2020 ◽  
Vol 635 ◽  
pp. L12 ◽  
Author(s):  
◽  
A. Caratti o Garatti ◽  
R. Fedriani ◽  
R. Garcia Lopez ◽  
M. Koutoulaki ◽  
...  
Keyword(s):  
Near Infrared ◽  
Major Axis ◽  
Position Angle ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Stellar Objects ◽  
Axis Position ◽  
The Continuum ◽  
Gaseous Disc

Context. The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved. Aims. We deploy near-infrared spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3–2.4 μm). Methods. We present the first GRAVITY/VLTI observations at high spectral (ℛ = 4000) and spatial (mas) resolution of the CO overtone transitions in NGC 2024 IRS 2. Results. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases (≤8°). Our best ellipsoid model provides a disc inclination of 34° ±1°, a disc major axis position angle (PA) of 166° ± 1°, and a disc diameter of 3.99 ± 0.09 mas (or 1.69  ±  0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.74±0.070.08 mas (1.16  ±  0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and PA matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of M* ∼ 14.7−3.6+2 M⊙ by combining our interferometric and spectral modelling results.

scholarly journals Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects – I. Revisiting the high-mass protostar W33A

2021 ◽  
Vol 503 (1) ◽  
pp. 270-291
Author(s):  
F Navarete ◽  
A Damineli ◽  
J E Steiner ◽  
R D Blum
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Rotation Axis ◽  
Principal Component ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Rotating Disc ◽  
Stellar Objects ◽  
K Band

ABSTRACT W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ $\rm {M}_\odot$ for the ‘disc + protostar’ system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar $\rm {H}_2$ jet aligned perpendicular to the rotation axis of W33A.

scholarly journals Planet formation in action: resolved gas and dust images of a transitional disk and its cavity

2013 ◽  
Vol 8 (S299) ◽  
pp. 90-93
Author(s):  
Nienke van der Marel ◽  
Ewine F. van Dishoeck ◽  
Simon Bruderer ◽  
Til Birnstiel ◽  
Paola Pinilla ◽  
...  
Keyword(s):  
Planet Formation ◽  
Early Stage ◽  
Continuum Emission ◽  
Dust Trapping ◽  
Spatially Resolved ◽  
First Results ◽  
Disk Evolution ◽  
Gas Cavity ◽  
Dust Distribution ◽  
The Continuum

AbstractPlanet formation and clearing of protoplanetary disks is one of the long standing problems in disk evolution theory. The best test of clearing scenarios is observing systems that are most likely to be actively forming planets: the transitional disks with large inner dust cavities. We present the first results of our ALMA (Atacama Large Millimeter/submillimeter Array) Cycle 0 program using Band 9, imaging the Herbig Ae star Oph IRS 48 in CO 6−5 and the submillimeter continuum in the extended configuration. The resulting ~0.2″ spatial resolution completely resolves the cavity of this disk in the gas and the dust. The gas cavity of IRS 48 is half as large as the dust cavity, ruling out grain growth and photoevaporation as the primary cause of the truncation. On the other hand, the continuum emission reveals an unexpected large azimuthal asymmetry and steep edges in the dust distribution along the ring, suggestive of dust trapping. We will discuss the implications of the combined gas and dust distribution for planet formation at a very early stage. This is one of the first transition disks with spatially resolved gas inside the cavity, demonstrating the superb capabilities of the Band 9 receivers.

scholarly journals Abundant, hot water toward young stellar objects

1997 ◽  
Vol 178 ◽  
pp. 397-400
Author(s):  
F.P. Helmich ◽  
E.F. Van Dishoeck ◽  
J.H. Black ◽  
Th. De Graauw
Keyword(s):  
Hot Water ◽  
Resolving Power ◽  
Young Stellar Objects ◽  
Small Scale ◽  
Interstellar Space ◽  
Infrared Space Observatory ◽  
Direct Estimate ◽  
Infrared Source ◽  
Stellar Objects ◽  
Star Forming

The large amount of water vapour in the Earth's atmosphere makes it extremely difficult to observe water in interstellar space, except under unusual conditions (e.g., masers). The Short Wavelength Spectrometer (SWS; de Graauw et al. 1996) on board the Infrared Space Observatory (ISO) provides an unique opportunity to study the ro-vibrational fundamental bands of water in absorption against bright infrared continuum sources. Such absorption line data have several advantages over emission observations. For example, only a pencil beam to the infrared source is probed, which minimizes the complications due to the small-scale physical and chemical heterogeneity of star-forming regions. In addition, lines from all rotational levels are present within a vibrational band, so that the complete spectrum yields a direct estimate of the level populations and excitation temperature along the line of sight. Other molecules, such as CO, HCN and C2H2, can be observed with the same technique, leading to accurate relative abundances. The main limitation of the ISO-SWS grating is its low spectral resolving power, λ/Δ λ ≈ 1350 at 6 μm, since the lines are intrinsically much narrower. This limits the sensitivity, so that only high column densities can be detected, and complicates the interpretation because detectable lines are often saturated. The low spectral resolution also blends the lines, making it difficult to determine the equivalent widths unambiguously. The ISO-SWS is therefore particularly sensitive to molecules in warm gas with relatively large line widths (Δ V > 3 km s−1).

Radio continuum emission from young stellar objects in L1641

1990 ◽  
Vol 362 ◽  
pp. 274 ◽  
Author(s):  
James A. Morgan ◽  
Ronald L. Snell ◽  
Karen M. Strom
Keyword(s):  
Radio Continuum ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Stellar Objects

scholarly journals Validating post-AGB candidates in the LMC and SMC using SALT spectra

2020 ◽  
Vol 641 ◽  
pp. A142
Author(s):  
R. Szczerba ◽  
M. Hajduk ◽  
Ya. V. Pavlenko ◽  
B. J. Hrivnak ◽  
B. M. Kaminsky ◽  
...  
Keyword(s):  
South African ◽  
Stellar Atmosphere ◽  
Magellanic Clouds ◽  
Emission Lines ◽  
Young Stellar Objects ◽  
Agb Stars ◽  
Large Telescope ◽  
Stellar Objects ◽  
Effective Temperatures ◽  
The Continuum

We selected a sample of post-AGB candidates in the Magellanic Clouds on the basis of their near- and mid-infrared colour characteristics. Fifteen of the most optically bright post-AGB candidates were observed with the South African Large Telescope in order to determine their stellar parameters and thus to validate or discriminate their nature as post-AGB objects in the Magellanic Clouds. The spectral types of absorption-line objects were estimated according to the MK classification, and effective temperatures were obtained by means of stellar atmosphere modelling. Emission-line objects were classified on the basis of the fluxes of the emission lines and the presence of the continuum. Out of 15 observed objects, only 4 appear to be genuine post-AGB stars (27%). In the SMC, 1 out of 4 is post-AGB, and in the LMC, 3 out 11 are post-AGB objects. Thus, we can conclude that the selected region in the colour-colour diagram, while selecting the genuine post-AGB objects, overlaps severely with other types of objects, in particular young stellar objects and planetary nebulae. Additional classification criteria are required to distinguish between post-AGB stars and other types of objects. In particular, photometry at far-IR wavelengths would greatly assist in distinguishing young stellar objects from evolved ones. On the other hand, we showed that the low-resolution optical spectra appear to be sufficient to determine whether the candidates are post-AGB objects.

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